Analysis of photon transit time for low-power light passing into the head, and through both skull and brain, of human subjects allowed for tomographic imaging of cerebral hemoglobin oxygenation based on photon diffusion theory. In healthy adults, imaging of changes in hemoglobin saturation during hand movement revealed focal, contralateral increases in motor cortex oxygenation with spatial agreement to activation maps determined by functional magnetic resonance imaging; in ill neonates, imaging of hemoglobin saturation revealed focal regions of low oxygenation after acute stroke, with spatial overlap to injury location determined by computed tomography scan. Because such slow optical changes occur over seconds and co-localize with magnetic resonance imaging vascular signals whereas fast activation-related optical changes occur over milliseconds and co-localize with EEG electrical signals, optical methods offer a single modality for exploring the spatio-temporal relationship between electrical and vascular responses in the brain in vivo, as well as for mapping cortical activation and oxygenation at the bedside in real-time for clinical monitoring.

We develop a clinical visible-light spectroscopy (VLS) tissue oximeter. Unlike currently approved near-infrared spectroscopy (NIRS) or pulse oximetry (SpO2%), VLS relies on locally absorbed, shallow-penetrating visible light (475 to 625 nm) for the monitoring of microvascular hemoglobin oxygen saturation (StO2%), allowing incorporation into therapeutic catheters and probes. A range of probes is developed, including noncontact wands, invasive catheters, and penetrating needles with injection ports. Data are collected from: 1. probes, standards, and reference solutions to optimize each component; 2. ex vivo hemoglobin solutions analyzed for StO2% and pO2 during deoxygenation; and 3. human subject skin and mucosal tissue surfaces. Results show that differential VLS allows extraction of features and minimization of scattering effects, in vitro VLS oximetry reproduces the expected sigmoid hemoglobin binding curve, and in vivo VLS spectroscopy of human tissue allows for real-time monitoring (e.g., gastrointestinal mucosal saturation 69+/-4%, n=804; gastrointestinal tumor saturation 45+/-23%, n=14; and p<0.0001), with reproducible values and small standard deviations (SDs) in normal tissues. FDA approved VLS systems began shipping earlier this year. We conclude that VLS is suitable for the real-time collection of spectroscopic and oximetric data from human tissues, and that a VLS oximeter has application to the monitoring of localized subsurface hemoglobin oxygen saturation in the microvascular tissue spaces of human subjects.

This study was designed to demonstrate the feasibility of MRI-guided radiofrequency ablation (RFA) of breast cancer. A total of three women diagnosed with invasive ductal breast cancer were treated with percutaneous MRI-guided RFA, according to a treat and resect protocol, in our hospital. RFA procedures were performed in an open 0.5T Signa-SP imager allowing direct patient access and realtime monitoring of the procedure. In all patients ablation was performed with a 15-gauge insulated MRI-compatible multiple needle probe. MRI thermometry and contrast-enhanced postablation MRI were used to evaluate the ablation process. Patients underwent lumpectomy within a week of the RFA procedure. Histopathology confirmed successful (100%) tumor ablation in one patient, and partial tumor destruction (33% and 50%, respectively) in two patients. Challenges of MRI-guided breast RFA that need to be solved to facilitate progress of the technique toward clinical practice are discussed. TECHNOLOGIC ADVANCES over the last decade have enabled investigations of minimally invasive ablation of primary breast malignancies (1,2). Percutaneous radiofrequency ablation (RFA), which was first reported for treatment of breast tumors in 1999, uses a multiplewire electrode to destroy tumor cells by thermal coagulation and protein denaturation (3-6). The experience with RFA in patients with breast carcinoma is still in the early stages of development. All previously reported studies assessing the accuracy of RFA of breast tumors used ultrasound (US) to guide the ablation probe (7-11). In general, these studies concluded that monitoring the ablation process utilizing real-time US was somewhat inaccurate, because the hyperechogenicity of the heated breast tissue and the ultrasonographic shadowing made it difficult to differentiate between ablated tissue and residual tumor (9,10).MRI may be a more suitable modality for targeted imaging of breast lesions during RFA (11). Of all imaging modalities, MRI has the highest accuracy for determining the size and extent of breast malignancies (12). Furthermore, MRI potentially allows real-time monitoring of the ablation process (13), which in turn has potential to provide intraprocedural assessment of the completeness of ablation, as well as whether any collateral structures are inadvertently heated. As a consequence, with open MRI systems currently commercially available, interest in MRI-guided tumor ablation techniques is growing. To our knowledge, MRI-guided RFA of malignant breast tumors has not been reported in humans. In this feasibility study, we present our initial experience in three patients and discuss the technical challenges of MRI-guided RFA of breast cancer. MATERIALS AND METHODSWe treated three female breast cancer patients (47, 45, and 60 years of age) with MRI-guided RFA in our hospital, according to a treat and resect protocol approved by our institution's human subjects panel. In all patients the tumor was primarily detected on conventional mammography and additional US as a solitary suspi...

No abstract

We report the development of a general, quantitative, and localized visible light clinical tissue oximeter, sensitive to both hypoxemia and ischemia. Monitor design and operation were optimized over four instrument generations. A range of clinical probes were developed, including non-contact wands, invasive catheters, and penetrating needles with injection ports. Real-time data were collected (a) from probes, standards, and reference solutions to optimize each component, (b) from ex vivo hemoglobin solutions co-analyzed for StO 2 % and pO 2 during deoxygenation, and (c) from normoxic human subject skin and mucosal tissue surfaces. Results show that (a) differential spectroscopy allows extraction of features with minimization of the effects of scattering, (b) in vitro oximetry produces a hemoglobin saturation binding curve of expected sigmoid shape and values, and (c) that monitoring human tissues allows real-time tissue spectroscopic features to be monitored. Unlike with near-infrared (NIRS) or pulse oximetry (SpO 2 %) methods, we found non-pulsatile, diffusion-based tissue oximetry (StO 2 %) to work most reliably for non-contact reflectance monitoring and for invasive catheter-or needle-based monitoring, using blue to orange light (475-600 nm). Measured values were insensitive to motion artifact. Down time was non-existent. We conclude that the T-Stat™ oximeter design is suitable for the collection of spectroscopic data from human subjects, and that the oximeter may have application in the monitoring of regional hemoglobin oxygen saturation in the capillary tissue spaces of human subjects.